/*
 * This file Copyright (C) 2015-2016 Mnemosyne LLC
 *
 * It may be used under the GNU GPL versions 2 or 3
 * or any future license endorsed by Mnemosyne LLC.
 *
 */

#include <errno.h>
#include <string.h> /* strcmp() */

#include <fcntl.h> /* open() */
#include <unistd.h> /* close() */

#include <sys/types.h>
#include <sys/event.h>

#ifndef O_EVTONLY
#define O_EVTONLY O_RDONLY
#endif

#include <event2/event.h>

#define __LIBTRANSMISSION_WATCHDIR_MODULE__

#include "transmission.h"
#include "log.h"
#include "ptrarray.h"
#include "tr-assert.h"
#include "utils.h"
#include "watchdir.h"
#include "watchdir-common.h"

/***
****
***/

#define log_error(...) (!tr_logLevelIsActive(TR_LOG_ERROR) ? (void)0 : \
    tr_logAddMessage(__FILE__, __LINE__, TR_LOG_ERROR, "watchdir:kqueue", __VA_ARGS__))

/***
****
***/

typedef struct tr_watchdir_kqueue
{
    tr_watchdir_backend base;

    int kq;
    int dirfd;
    struct event* event;
    tr_ptrArray dir_entries;
}
tr_watchdir_kqueue;

#define BACKEND_UPCAST(b) ((tr_watchdir_kqueue*)(b))

#define KQUEUE_WATCH_MASK (NOTE_WRITE | NOTE_EXTEND)

/***
****
***/

static void tr_watchdir_kqueue_on_event(evutil_socket_t fd UNUSED, short type UNUSED, void* context)
{
    tr_watchdir_t const handle = context;
    tr_watchdir_kqueue* const backend = BACKEND_UPCAST(tr_watchdir_get_backend(handle));
    struct kevent ke;
    struct timespec const ts = { .tv_sec = 0, .tv_nsec = 0 };

    if (kevent(backend->kq, NULL, 0, &ke, 1, &ts) == -1)
    {
        log_error("Failed to fetch kevent: %s", tr_strerror(errno));
        return;
    }

    /* Read directory with generic scan */
    tr_watchdir_scan(handle, &backend->dir_entries);
}

static void tr_watchdir_kqueue_free(tr_watchdir_backend* backend_base)
{
    tr_watchdir_kqueue* const backend = BACKEND_UPCAST(backend_base);

    if (backend == NULL)
    {
        return;
    }

    TR_ASSERT(backend->base.free_func == &tr_watchdir_kqueue_free);

    if (backend->event != NULL)
    {
        event_del(backend->event);
        event_free(backend->event);
    }

    if (backend->kq != -1)
    {
        close(backend->kq);
    }

    if (backend->dirfd != -1)
    {
        close(backend->dirfd);
    }

    tr_ptrArrayDestruct(&backend->dir_entries, &tr_free);

    tr_free(backend);
}

tr_watchdir_backend* tr_watchdir_kqueue_new(tr_watchdir_t handle)
{
    char const* const path = tr_watchdir_get_path(handle);
    struct kevent ke;
    tr_watchdir_kqueue* backend;

    backend = tr_new0(tr_watchdir_kqueue, 1);
    backend->base.free_func = &tr_watchdir_kqueue_free;
    backend->kq = -1;
    backend->dirfd = -1;

    if ((backend->kq = kqueue()) == -1)
    {
        log_error("Failed to start kqueue");
        goto fail;
    }

    /* Open fd for watching */
    if ((backend->dirfd = open(path, O_RDONLY | O_EVTONLY)) == -1)
    {
        log_error("Failed to passively watch directory \"%s\": %s", path, tr_strerror(errno));
        goto fail;
    }

    /* Register kevent filter with kqueue descriptor */
    EV_SET(&ke, backend->dirfd, EVFILT_VNODE, EV_ADD | EV_ENABLE | EV_CLEAR, KQUEUE_WATCH_MASK, 0, NULL);

    if (kevent(backend->kq, &ke, 1, NULL, 0, NULL) == -1)
    {
        log_error("Failed to set directory event filter with fd %d: %s", backend->kq, tr_strerror(errno));
        goto fail;
    }

    /* Create libevent task for event descriptor */
    if ((backend->event = event_new(tr_watchdir_get_event_base(handle), backend->kq, EV_READ | EV_ET | EV_PERSIST,
            &tr_watchdir_kqueue_on_event, handle)) == NULL)
    {
        log_error("Failed to create event: %s", tr_strerror(errno));
        goto fail;
    }

    if (event_add(backend->event, NULL) == -1)
    {
        log_error("Failed to add event: %s", tr_strerror(errno));
        goto fail;
    }

    /* Trigger one event for the initial scan */
    event_active(backend->event, EV_READ, 0);

    return BACKEND_DOWNCAST(backend);

fail:
    tr_watchdir_kqueue_free(BACKEND_DOWNCAST(backend));
    return NULL;
}
